If we "all agree" and do a moonshot construction plan we could have electricity in 8 years. This is a fantasy, tho.
Best case scenario in the real world is operational in 12 years.
In the capitalist hellscape here in the US, a reasonable expectation would be 18-20 years.
20 years also happens to be the lifespan of our wind turbines. In 20 years, all of the currently running wind turbine blades will be in a landfill and new ones will need to be manufactured to replace them.
No reasonable person is suggesting nuclear as a short-term option. It's a long term investment.